Compilers - every programming language uses this. Databases - Btrees, indexes, distributed key value stores. The world runs on databases. Graphics - if you li

Compilers - every programming language uses this. Databases - Btrees, indexes, distributed key value stores. The world runs on databases. Graphics - if you like games, how a 3D scene is rendered, photo realism with Ray tracers, GPU pipelines and OpenGL AI and Machine Learning - tons of fascinating problems and algorithms. I’d say focus on the basics. Hash tables have remained mostly the same since they were invented. C still uses pointers, the basics are fundamentally so powerful that they are kind of eternal. When I hire someone, i’m looking for someone with strong fundamentals. They understand the basic datastructures, algorithms and how a computer works.